1. Field of the Invention
The invention relates to syringes and more particularly to an improved blood gas syringe.
2. Brief Description of the Prior Art
The prior art is replete with descriptions of syringes and their construction; see for example U.S. Pat. Nos. 2,869,543; 3,076,456, and 3,570,486. In spite of the highly developed state of the art a number of problems have heretofore been associated with the available syringes, particularly blood gas syringes. For example, often when expelling a "filler" material from a syringe, by exerting pressure on the plunger, there is a "rebound" of the plunger when pressure is terminated. This is undesirable, particularly for a blood gas collecting syringe, because it will serve to draw air back into the syringe thereby contaminating the blood specimen being collected.
The improved syringe of the invention cannot inadvertently "rebound". In addition, in the preferred syringes of the invention, arterial pressure is sufficient to activate the withdrawal of the plunger as an aid indicating when an artery has been entered.